Plating expanded boreholes

ABSTRACT

A well treatment method for consolidating an incompetent material in and/or around a borehole which includes the steps of hydraulically expanding a selected interval of the borehole opposite an unconsolidated formation by injecting a fluid into the interval at a fluid injection pressure less than, but approaching, the formation fracturing pressure and then injecting into the formation at substantially the same injection pressure a fluid containing electroless metal plating components the reaction products of which form a metal plating on the incompetent material.

United States Patent 1 Suman, Jr. et al.

[54] PLATING EXPANDED BOREHOLES [75] Inventors: George 0. Suman, Jr., Carey Epps Murphey, Jr., Edwin Allen Richardson, Robert Steven Torrest, all of Houston, Tex.

[73] Assignee: Shell Oil Company, New York,

22 Filed: 11111.7, 1971 21 Appl.No.:104, 695

[52] US. Cl ..l66/278, 166/292 [51] Int. Cl ..E2lb 33/138, E2lb 43/02 [58] Field of Search ..l66/250, 292, 278, 276, 300,

[56] References Cited UNITED STATES PATENTS 3/1970 Simpson ..166/292 7/1968 Richardson 1 1 Jan. 9, 197 3- 3,438,440 4/1969 Richardson ,.1 66/292 3,438,441 4/1969 Richardson ....l66/292 3,362,475 1/1968 Huitt et al. ....l66/278 3,587,741 6/1971 Primary Examiner-Stephen J. Novosad Attorney-Harold L. Denkler and Theodore E. Bieber ,7 ABSTRACT A well treatment method for consolidating an incompetent material in and/or around a borehole which includes the steps of hydraulically expanding a selected interval of the borehole opposite an unconsolidated formation by injecting a fluid into the interval at a fluid injection pressure less than, but approaching, the formation fracturing pressure and then injecting'into the formation at substantially the same injection pressure a fluid containing electroless metal plating components the reaction products of which form a metal plating on the incompetent material. 7

6 Claims, 1 Drawing Figure Casey l 66/278 1 PLATING EXPANDED BOREHOLES BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a process for treating unconsolidated subsurface formations and, more particularly, to treatment of loose or incompetent material in and around well bores so as to consolidate such material.

2. Description of the Prior Art In producing fluids such as petroleum from wells completed into unconsolidated subsurface earth formations, it is common to encounter operating problems caused by the sloughing of sand from the walls of the well bore. Among the methods used to prevent such sloughing is the consolidation of the incompetent formation by electroless plating techniques such as those described in US. Pat. Nos. 3,393,737; 3,438,440; and 3,438,441 to E. A. Richardson and in a copending application of E. A. Richardson and R. S. Torrest, Ser. No. 835,243, filed June 20,1969.

According to these electroless plating techniques, the constituent particles of the incompetent formation are bound together by a metal plating deposited on the particles in a chemical-reduction process to form a porous, permeable consolidated medium. These techniques generally involve the injection into the formation to be consolidated of a solution containing a catalytic activator followed by the injection of a plating solution containing a metal ion and a reducing agent which react in the presence of the catalyst to form a metal plating on the incompetent material.

SUMMARY OF THE INVENTION The present invention provides an improved method for consolidating an incompetent material in or surrounding a wellbore by electroless metal plating. According to the method, before solutions containing plating components are injected into the formation, the borehole is hydraulically expanded by injecting a viscous fluid into and/or against the formation at a pressure which approaches, but is less than, the formation fracturing pressure. The plating solutions are then injected at ratessufficient to maintain this borehole expanding pressure at least until enough of the components have entered the formation to consolidate the first contacted portions thereof. According to a preferred embodiment of the invention, the solutions necessary to the plating process are thickened with a suitable thickening agent to increase their effective viscosities and, thus, reduce the injection rate required to achieve the desired borehole expanding pressure.

BRIEF DESCRIPTION OF'THE DRAWING tubular casing 13 extends down the wellbore from the surface 14 to the bottom of the well 15. The casing 13 is fixed in place by means of a cement 16. The well 10 is in fluid communication with the formation 12 through a number of perforations 17 which penetrate the casing 13 and cement 16. a

To consolidate the formation 12 into a competent, porous and permeable medium according to the method of this invention, an enclosed path for fluid from a location on the surface 14 to the formation 12 is provided. For example, a tubing 18 may be extended into the well to a point adjacent a selected interval 19 of the borehole 11 which is adjacent the formation 12 to be treated. A closure means such as packer 20 may be installed in the borehole 11 above the interval 19 to be treated to close the annular space 21 between the casing 13 and tubing 18 to fluid flow thus preventing any fluid pumped down the tubing 18 from flowing into the annular space 21 above the closure means. The borehole preferably is closed below the interval to be packed, for example, by cement l6 and the bottom of the well 15 as is shown in the figure, or by other suitable pack-off or closure means such asbridge plug. At

the surface, the tubing 18 is operatively connected to a conduit means such as pipe 22 which is adapted to carry fluid from a pump means 23 to the tubing 18.

According to the method of this invention, the formation 12 is hydraulically expanded by pumping a fluid (hereinafter sometimes referred to as first fluid) which may be a catalytic activator containing solution capable of activating the grains of the formation forelectroless metal plating, from the pump means 23 through pipe 22, down the tubing 18 and into and/or against the formation 12 at an injection pressure lower than the fracturing pressure of the formation 12 but great enough to hydraulically expand the borehole 11 by compressing the formation 12 adjacent the borehole 11..This injection pressure is preferably great enough to cause the walls of the borehole 11 in the formation interval 19 to move outwardly relative to the cemented casing 13, thus opening a narrow space or cylindrical fracture'24 between the formation 12 and the cement 16 which cylindrical fracture 24 substantially surrounds the cemented casing 13.

After the borehole 11 has been hydraulically expanded to form the cylindrical fracture 24, any electroless metal plating solution or series of solutions containing activating and/or plating components suitable for use in the formation 12 may be injected into the expanded borehole 11, preferably at a fluid injection The FIGURE shows a diagramatic view partially in cross section of a well suitably equipped for the practice of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the FIGURE, we see a well 10 having a borehole 11 which penetrates a fluid-bearing earth formation 12 composed of unconsolidated particulate pressure substantially equal to the injection pressure used to hydraulically expand the borehole. For example, depending upon the formation temperature, the fluids injected may be chosen from those solutions described in U.S. Pat. Nos. 3,393,737; 3,438,440; and 3,438,441.

In a preferred embodiment of this invention, the injection pressure is maintained substantially constant as the injected fluid is changed from the firstfluid to a fluid containing components the reaction products of which form a metal plating on the grains of the material to be consolidated. However, it should be understood that the injection pressure into the formation 12 may be reduced after the cylindrical fracture 24 is opened with the first fluid and then re-established at the borehole expanding pressure just prior to the entry of the consolidating components. ln either case, once injection of plating components commences, the injection pressure is preferably maintained substantially into the formation 12 in an amount sufficient to consolidate the first contacted portions of the formation, and may advantageously be maintainedsubstantially constant ,throughout the plating process.

I Upon consolidation of the compressed formation by electroless plating, the formation is held in its compressed condition by the deposited metallic cementing material. Thus, the cylindrical fracture 24 between the formation 12 and cement 16 substantially remains open after the fluid injection pressure is reduced. The well 10, therefore, retains any improved injectivity (or correspondingly, productivity) which results from the opening of the cylindrical fracture 24.

As used herein, injection pressure" refers to the pressure in theborehole 11 at the face of the formation 12 into which fluid is injected. Those skilled in the art will have no problem determining the necessary surface pumping pressure required to achieve a given injection pressure."

The fracturing pressure of the formation 12, which is the upperlirnit of the fluid injection pressure preferably To determine a borehole expanding fluid injection pressure, less than the fracturing pressure of the formation 12, which is sufficient to open a cylindrical fracture 22 around the cemented casing 13, one may measure the injectivity of the perforated interval 19 as a function of injection pressure as by injecting a fluid into the formation 12 at an injection pressure near the average pressure of the fluids trapped in the formation 12 and then gradually increasing the injection pressure while measuring both the injection pressure and the in jection rate. Tests show that the injectivity (which for this purpose may be taken to be the ratio of the injection rate to the difference between the injection pressure and the average pressure in the formation 12) of a well increases markedly (generallyby a factor of 2 or more) when cylindrical fracture is formed in the injection interval and then remains substantially stable as pressure is increased up to the formation fracturing pressure. This improved injectivity may be attributed to the increased area of formation face presented to fluid flow upon the opening of the cylindrical fracture.

Thus, a pressure sufficient for forming a cylindrical fracture outside a cemented well casing may be determined by determining at what pressure'less than the fracturing pressure the injectivity of the well increases markedly. A preferred injection pressure for hydraulically expanding a borehole according to the method of this invention is one less than the fracturing pressure of the formation but within the range of pressures at which the injectivity has a relatively high and stable value. v

' As is well known in the art, the chemical reactions employed in electroless plating are often temperature dependent. Therefore, it is beneficial to employ a plating solution designed for maximum effectiveness at the prevailing temperature in the formation 12 to be consolidated. This temperature may bedetermined by well-known methods. However, if a large-volume of a fluid havinga temperature difierent from that of the formation 12 is injected into the formation to hydraulically expand the borehole, it becomes more difficult to determine the design temperature for the electroless plating process. Therefore, according to a preferred embodiment of the invention, at least some of the fluids to be injected are first treated with a thickening or viscosity enhancing agent such as a natural gum or a high molecular weight polymeric material in an amount sufficient to increase the effective viscosity of the fluid at the temperature of the formation 12, preferably to 5 to 15 times the viscosity of water at that temperature. This will reduce the injection rate required to achieve a given injection pressure with such a fluid and thus decrease the amount of that fluid which must be injected in the process of hydraulically expanding the borehole. It is-particularly advantageous to provide a first fluid having a viscosity of this order.

While the invention has been particularly with respect to treating an unconsolidated earth formation behind a cemented and perforated casing, it should be understood that the method is also applicable to the consolidation of the grains of a sand or gravel pack behind cemented or uncemented perforate casing in a well in which such a pack is installed. The method is particularly applicable to the consolidation of a pack installed according to the method of a copending, commonly assigned, application of C. E. Murphey, Jr., T. A. Simon, and R. S. Torrest, Ser. No. 082,925, filed Oct. 22, l970. One embodiment of the Murphey et al. packing method comprises the steps of pumping a slurry of a packing material such as sand through the end of a tubing string that is extended to a point adjacent the bottom of an interval to be packed ina cemented and perforated casing, adjusting the slurry-pumping pressure to maintain a pressure in the interval sufficient to create a cylindrical fracture around the cement, and simultaneously raising the tubing string at a rate that is correlated withthe pumping rate in order to maintain a fluidized bed of sand around the end of the tubing string as it moves through the interval to be packed. In using this packing method in conjunction with the incompetent material consolidation process of the present invention, the slurry of sand may be considered the first fluid (as defined above) which is used to initially expand the borehole. After placement of the sand pack, the sand in the expanded borehole and at least some of the surrounding compressed earth formation may be consolidated by injecting activating and/or plating solutions for electroless metal plating according to the method described above. I

The method of this invention is also applicable to electroless metal plating in uncased boreholes and in boreholes cased with uncemented perforate casing such as a slotted liner. In these boreholes, of course, no cylindrical fracture is formed when plating according to the method of this invention. However, it is advantageous to hydraulically expand such boreholes prior to the injection of plating solution because the consolidation of the compressed formation material around such an expanded borehole forms a high strength, prestressed "cemented" cylinder which is especially resistant to cracking and chipping. In addidescribed 9 tion, the flow performance of some wells may be enhanced because the expanded borehole has a greater surface area open to flow from the adjacent formation than does a non-expanded borehole.

In summary, in a well having a borehole which extends into an earth formation at least in part composed of unconsolidated particulate matter, the present invention provides an electroless metal plating method for consolidatinginto a competent, porous and permeable medium at least some of the particulate matter comprising the steps of: hydraulically expanding a selected interval of the' borehole opposite the formation by injecting a fluid which may be a solution containing a catalytic activator for electroless metal plating into the interval at a borehole expanding fluid injection pressure less than the formation fracture pressure; and maintaining the fluid injection pressure substantially constant at least until electroless metal plating components have been injected in an amount sufiicient to consolidate the first contacted portions of the formation adjacent the borehole. The method may include the step of packing the selected interval of the borehole with a pack of granular material before injecting the fluid containing electroless metal plating components. A preferred embodiment of the invention includes the step of adding a viscosity enhancing agent to the catalytic activator containing fluid and/or to the fluid containing electroless metal plating components in an amount sufficient to increase the effective viscosity of water.

In a well having a borehole lined with a tubular casing which is fixed in place with a cement and perforated with a number of perforations through a selected interval of the borehole opposite an earth formation at least in part composed of an unconsolidated particulate matter, the invention provides an electroless metal plating method for consolidating at least some of the particulate matter comprising the steps of: enclosing the selected interval of the borehole by providing a substantially fluid-tight pack-off means in the borehole above and below the selected interval; providing a flow path for pumping a fluid under pressure from a surface location into the selected interval of the borehole; determining a cylindrical fracture forming pressure less than the lateral fracturing pressure of said earth formation which is sufficient to cause the surrounding earth formation to move outwardly relative to the cemented string of easing leaving a narrow space between the cement and the earth formation; hydraulically expanding the selected interval of the borehole by injecting a fluid into said selected interval at a borehole expanding fluid injection pressure substantially equal to said cylindrical fracturing pressure; injecting into the formation a fluid containing electroless metal plating components, the reaction products of which form a metal plating on said particulate matter, at a fluid injection pressure substantially equal to the borehole expanding fluid injection pressure; and maintaining the fluid injection pressure substantially constant at least until electroless metal plating components have been injected in an amount sufiicient to consolidate the first contacted portions of the formation adjacent the borehole.

We claim as our invention: 1. In a well having a borehole which extends into an earth formation at least in part composed of unconsolidated particulate matter an electroless metal plating method for consolidating at least some of said particulate matter comprising the steps of:

hydraulically expanding a selected interval. of th borehole opposite said formation by injecting a first fluid into said formation at a borehole expanding fluid injection pressure that is less than the formation fracturing pressure but is within the range of pressures at which the injectivity has a relatively high and stable value; injecting into the formation a fluid containing electroless metal plating components, the reaction products of which form a metal plating on said particulate matter, at a fluid injection pressure substantially constant at least until electroless metal plating components have been injected in an amount sufficient to consolidate the first contacted portions of the formation adjacent the borehole.

2. The method of claim 1 wherein the first fluid is a solution containing catalytic activator for electroless metal plating.

3. The method claim 1 including the step of packing said selected interval of the borehole with a pack of granular material before injecting said fluid containing electroless metal plating components.

4. The method of claim 1 including the step of adding a viscosity enhancing agent to at least some of said fluids injected into said formation in an amount sufficient to increase the effective viscosity of said fluid in the formation to a viscosity between 5 and 15 times the viscosity of water. I

5. in a well having a borehole lined with a tubular casing which is fixed in place with a cement and perforated with a number of perforations through a selected interval of the borehole opposite an earth formation at least in part composed of an unconsolidated particulate matter, an electroless metal plating method for consolidating at least some of said particulate matter comprising the steps of:

providing a flow path for pumping a fluid under pressure from a surface location into the selected interval of the borehole; determining a cylindrical fracture forming pressure less than the lateral fracturing pressure of said earth formation which is sufficient to cause the' surrounding earth formation to move outwardly relative to the cemented string of casing leaving a narrow space between the cement and the earth formation; I

hydraulically expanding said selected interval of the borehole by injecting a fluid into said selected interval at a borehole expanding fluid injection pressure substantially equal to said cylindrical fracturing pressure; I

injecting into the formation a fluid containing elecp 7 3,709,299 7 6. The method of claim including the step of packing said selected interval of the borehole with a pack of granular material before injecting said fluid' I containing electroless metal plating components.

t'iitt .5 

2. The method of claim 1 wherein the first fluid is a solution containing catalytic activator for electroless metal plating.
 3. The method claim 1 including the step of packing said selected interval of the borehole with a pack of granular material before injecting said fluid containing electroless metal plating components.
 4. The method of claim 1 including the step of adding a viscosity enhancing agent to at least some of said fluids injected into said formation in an amount sufficient to increase the effective viscosity of said fluid in the formation to a viscosity between 5 and 15 times the viscosity of water.
 5. in a well having a borehole lined with a tubular casing which is fixed in place with a cement and perforated with a number of perforations through a selected interval of the borehole opposite an earth formation at least in part composed of an unconsolidated particulate matter, an electroless metal plating method for consolidating at least some of said particulate matter comprising the steps of: providinG a flow path for pumping a fluid under pressure from a surface location into the selected interval of the borehole; determining a cylindrical fracture forming pressure less than the lateral fracturing pressure of said earth formation which is sufficient to cause the surrounding earth formation to move outwardly relative to the cemented string of casing leaving a narrow space between the cement and the earth formation; hydraulically expanding said selected interval of the borehole by injecting a fluid into said selected interval at a borehole expanding fluid injection pressure substantially equal to said cylindrical fracturing pressure; injecting into the formation a fluid containing electroless metal plating components, the reaction products of which form a metal plating on said particulate matter, at a fluid injection pressure substantially equal to said borehole expanding fluid injection pressure; and maintaining said fluid injection pressure substantially constant at least until electroless metal plating components have been injected in an amount sufficient to consolidate the first contacted portions of the formation adjacent the borehole.
 6. The method of claim 5 including the step of packing said selected interval of the borehole with a pack of granular material before injecting said fluid containing electroless metal plating components. 